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Mechanisms of Failure from Surface Flaws in Mixed‐Mode Loading
Author(s) -
MARSHALL DAVID B.
Publication year - 1984
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1984.tb09626.x
Subject(s) - indentation , materials science , residual stress , fracture mechanics , acoustic emission , composite material , machining , fracture (geology) , shear (geology) , failure mode and effects analysis , structural engineering , metallurgy , engineering
Mechanisms of failure from surface cracks in combined tension and shear are identified by directly observing the cracks during failure testing. Under the combined influences of residual contact stresses and applied loading, indentation cracks propagate stably and realign normal to the principal applied tension prior to failure. Annealing of indentation flaws causes relaxation of the residual stresses and thereby leads to a change in the mechanics of fracture; unstable propagation occurs from the initial crack at a critical applied loading, with an abrupt change in fracture plane. Strengths of indentation flaws and machining damage in both the as‐formed and annealed states are measured as a function of flaw orientation relative to an applied uniaxial tension. Strength variations of indentations and machining flaws are similar. The results are assessed in terms of various proposed mixed‐mode fracture criteria, and the implications of the results for nondestructive testing using scattering of surface acoustic waves are discussed.